According to a Transmission Control Protocol (TCP), successful transmission of a segment is confirmed only after an ACK packet for the transmission is received when the ACK packet is not received for a predetermined time set up in a timer after the transmission of a segment, the segment is transmitted again. Herein, the timer is called a retransmission timer.
Also, when a receiving part receives a segment, an ACK packet for the reception should be transmitted. When the ACK packet is transmitted, a plurality of segments are received and all ACK informations for the segments are loaded in one packet and transmitted to raise efficiency instead of a method for transmitting on ACK packet for each segment. However, the receiving part receives a first segment, which does not transmit the ACK packet and sets up a timer to prevent excess of the retransmission timer in a transmitting part. Accordingly, when the timer exceeds, the receiving part unconditionally transmits the ACK packet.
A protocol stack of an operating system is generally in charge of conventional TCP processing and software manages the timers. The above-mentioned retransmission timer and the delayed ACK timer are required for every activated channel, and searching a timer table can be considerable overhead as the number of simultaneous connection increases.